A British infosec company has found that cheap thermal imaging accessories for smartphones can be used to glean personal identification numbers entered on push-button security devices on bank ATMs..

Thermal imaging devices used to be bulky and expensive, but Sec-Tec told iTnews they can now be bought cheaply as compact iPhone accessories – for instance, the FLIR One, which retails for US$249 (A$340).

The company tested several PIN pads in ATMs, locks and safes with the thermal imagers and found they could “leak” the digits entered by legimate users for longer than a minute after use.

Cheap thermal imagers can steal user PINs